Not 5/16-18 or 5/16-24. Not 8MM nor 10MM

6141 Views 17 Replies 8 Participants Last post by RED-85-Z51, Jan 29, 2012

Obscured_by_Clouds

Discussion Starter · Jan 25, 2012

So what is it?

Trying to replace a stripped out chain tensioner on a Homelite chainsaw. I guess it was a softer metal that the stud and the first few threads gave way.

A 5/16-18 nut starts on the stud, but only goes a few turns, then jams. 5/16-24 won't go that far. 8MM is too small, 10MM is too big.

Thought maybe the stud threads were partially bunged and maybe I could chase them with a die. No go there either. Die won't start to thread on at all and I don't want to force it and crosscut the threads.

I've got it jerry-rigged for now using a backing spacer and a nut forced on as far as I can get it. It's tight and safe, but not the way it should be. Hopefully I can find a replacement OEM part, but that might be awhile before I get back to town.

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RED-85-Z51

· #2 · Jan 25, 2012

Model number, spec number..picture...need more info on this one.

RedOctobyr

· #3 · Jan 25, 2012

If you have an assortment of bolts, or a tap set, can you see what pitch the thread is? That might at least help point things in the right direction. Hold, say, a 1/4-20 tap against the side of the stud. Even if the stud were, say, 1/2-20 (for discussion), the 1/4-20 tap would slip "cleanly" into the grooves on the stud, and you'd know that both were -20 pitch.

If you have calipers, you could also check the outside diameter of the stud threads, which might help give a clue.

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wilber

· #4 · Jan 26, 2012

What is the diameter of the stud?
8mm is .315"
5/16" is .3125"
9mm is .354"

Measure pitch. How did you determine 8mm was wrong? There are more than 1 pitches for 8mm.

W

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themidniteryder

· #5 · Jan 26, 2012

Machine screw threads?

Obscured_by_Clouds

Discussion Starter · #6 · Jan 26, 2012 (Edited)

How did you determine 8mm was wrong?

Test fit at a hardware store. 8MM doesn't begin to thread in. Store I was at only fine or coarse, but I don't remember the numbers. 10MM doesn't begin to go in. They didn't have any 9MM if anyone even makes those.

If you have an assortment of bolts, or a tap set, can you see what pitch the thread is?

Thread gauge lines up best on 20/in, but a 1/4-20 slips through and I couldn't find a 5/16-20 bolt to try.

Saw is a 14in, 35CC Homelite

Stripped nut in question is inside the yellow tensioner just above the '5' in this picture. Tensioner may not be the right term. This turns to hold the bar in place after adjusting the chain tension using the yellow thumbwheel just above the '3' in the picture.

Machine screw threads?

Possibility, but what would the equivalent be? #10? #12?

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wilber

· #7 · Jan 26, 2012

Obscured_by_Clouds said:
Test fit at a hardware store. 8MM doesn't begin to thread in. Store I was at only fine or coarse, but I don't remember the numbers. 10MM doesn't begin to go in. They didn't have any 9MM if anyone even makes those.

Thread gauge lines up best on 20/in, but a 1/4-20 slips through and I couldn't find a 5/16-20 bolt to try.

Saw is a 14in, 35CC Homelite

Stripped nut in question is inside the yellow tensioner just above the '5' in this picture. Tensioner may not be the right term. This turns to hold the bar in place after adjusting the chain tension using the yellow thumbwheel just above the '3' in the picture.

Possibility, but what would the equivalent be? #10? #12?

10/24 10/32 is smaller than1/4" that puts it out of the possibility.

12/24 12/28 is smaller than1/4" that puts it out of the possibility also.

8mm comes in .50mm and 1.00mm pitch
9mm comes in same pitch.

W

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RED-85-Z51

· #8 · Jan 26, 2012 (Edited)

Homelite P/N: 678618002

http://www.ereplacementparts.com/tension-nut-p-543856.html

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wilber

· #9 · Jan 26, 2012

RED-85-Z51 said:
Homelite P/N: 678618002

http://www.ereplacementparts.com/tension-nut-p-543856.html

"Amen" what would he do with a nut ???

W

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Obscured_by_Clouds

Discussion Starter · #10 · Jan 26, 2012

wilber said:
what would he do with a nut ???

Actually, I got a threaded rod coupler and with the help of a washer, it works quite well. I can get it turned on enough threads to keep it in place and be safe.

I hadn't gotten around to looking for the real part yet and just needed something quick and dirty short-term.

I'll check my local shop when I get to town in a few days and if they don't have it, I'll have to order one. Maybe two so I'll have a spare.

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38racing

· #11 · Jan 26, 2012

wilber said:
"Amen" what would he do with a nut ???

W

I'm guessing that part has a nut inside and arms are for applying manual torque

LouMG

· #12 · Jan 26, 2012

There are 13 different pitches available as hand taps for a 5/16 Dia. from 18 to 80. 18 and 24 are just the common ones.

RED-85-Z51

· #13 · Jan 27, 2012

Its going to be Metric...those saws are Made in China..

Obscured_by_Clouds

Discussion Starter · #14 · Jan 28, 2012

I figured it might be metric, but I can't find a 9MM bolt or nut locally to try it, nor have I seen a 5/16-20 which looks like it might fit.

Anyways, I should be able to get the t-bar part this week.

Anybody know if this will take an 18 or 20" bar? The 14 just won't quite handle the trunk I have to deal with and I really can't see buying a larger saw that I might never need again. No rental places close by either.

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RedOctobyr

· #15 · Jan 28, 2012

35cc with a stock 14" bar, going up to 18-20" sounds like that may be a bit much. But I suppose it depends on what kind of wood you're cutting, etc. If you let it go slowly, maybe it would be OK. I wouldn't try to "force" it; if the engine starts to bog down, maybe take some pressure off the blade?

I have an old Stihl with a 51cc engine, it was available with bars up to 20", as a point of comparison.

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RED-85-Z51

· #16 · Jan 28, 2012

35cc is about tapped out with 14".

40cc is the minimum really for 16", 42-45 for 18" and 50 for 20".

MrGiggles

· #17 · Jan 29, 2012

You could try running an 18" with a skip chain... But I've cut 30" oak rounds with a 14" McCulloch. Just need to go slow and keep the cut straight.

RED-85-Z51

· #18 · Jan 29, 2012

Do they make a 3/8LP skip or semi skip?

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